[PATCH 06/15] run-command API: have "run_processes_parallel{,_tr2}()" return void

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Change the "run_processes_parallel{,_tr2}()" functions to return void,
instead of int. Ever since c553c72eed6 (run-command: add an
asynchronous parallel child processor, 2015-12-15) they have
unconditionally returned 0.

To get a "real" return value out of this function the caller needs to
get it via the "task_finished_fn" callback, see the example in hook.c
added in 96e7225b310 (hook: add 'run' subcommand, 2021-12-22).

So the "result = " and "if (!result)" code added to "builtin/fetch.c"
d54dea77dba (fetch: let --jobs=<n> parallelize --multiple, too,
2019-10-05) has always been redundant, we always took that "if"
path. Likewise the "ret =" in "t/helper/test-run-command.c" added in
be5d88e1128 (test-tool run-command: learn to run (parts of) the
testsuite, 2019-10-04) wasn't used, instead we got the return value
from the "if (suite.failed.nr > 0)" block seen in the context.

Subsequent commits will alter this API interface, getting rid of this
always-zero return value makes it easier to understand those changes.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 builtin/fetch.c             | 17 ++++++++---------
 run-command.c               | 27 +++++++++++----------------
 run-command.h               | 16 ++++++++--------
 t/helper/test-run-command.c |  4 ++--
 4 files changed, 29 insertions(+), 35 deletions(-)

diff --git a/builtin/fetch.c b/builtin/fetch.c
index a0fca93bb6a..78043fb67ef 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -1953,15 +1953,14 @@ static int fetch_multiple(struct string_list *list, int max_children)
 		struct parallel_fetch_state state = { argv.v, list, 0, 0 };
 
 		strvec_push(&argv, "--end-of-options");
-		result = run_processes_parallel_tr2(max_children,
-						    &fetch_next_remote,
-						    &fetch_failed_to_start,
-						    &fetch_finished,
-						    &state,
-						    "fetch", "parallel/fetch");
-
-		if (!result)
-			result = state.result;
+		run_processes_parallel_tr2(max_children,
+					   &fetch_next_remote,
+					   &fetch_failed_to_start,
+					   &fetch_finished,
+					   &state,
+					   "fetch", "parallel/fetch");
+
+		result = state.result;
 	} else
 		for (i = 0; i < list->nr; i++) {
 			const char *name = list->items[i].string;
diff --git a/run-command.c b/run-command.c
index 5ec3a46dccf..642e6b6e057 100644
--- a/run-command.c
+++ b/run-command.c
@@ -1783,11 +1783,11 @@ static int pp_collect_finished(struct parallel_processes *pp)
 	return result;
 }
 
-int run_processes_parallel(int n,
-			   get_next_task_fn get_next_task,
-			   start_failure_fn start_failure,
-			   task_finished_fn task_finished,
-			   void *pp_cb)
+void run_processes_parallel(int n,
+			    get_next_task_fn get_next_task,
+			    start_failure_fn start_failure,
+			    task_finished_fn task_finished,
+			    void *pp_cb)
 {
 	int i, code;
 	int output_timeout = 100;
@@ -1834,25 +1834,20 @@ int run_processes_parallel(int n,
 	}
 
 	pp_cleanup(&pp);
-	return 0;
 }
 
-int run_processes_parallel_tr2(int n, get_next_task_fn get_next_task,
-			       start_failure_fn start_failure,
-			       task_finished_fn task_finished, void *pp_cb,
-			       const char *tr2_category, const char *tr2_label)
+void run_processes_parallel_tr2(int n, get_next_task_fn get_next_task,
+				start_failure_fn start_failure,
+				task_finished_fn task_finished, void *pp_cb,
+				const char *tr2_category, const char *tr2_label)
 {
-	int result;
-
 	trace2_region_enter_printf(tr2_category, tr2_label, NULL, "max:%d",
 				   ((n < 1) ? online_cpus() : n));
 
-	result = run_processes_parallel(n, get_next_task, start_failure,
-					task_finished, pp_cb);
+	run_processes_parallel(n, get_next_task, start_failure,
+			       task_finished, pp_cb);
 
 	trace2_region_leave(tr2_category, tr2_label, NULL);
-
-	return result;
 }
 
 int run_auto_maintenance(int quiet)
diff --git a/run-command.h b/run-command.h
index 0e85e5846a5..e76a1b6b5b3 100644
--- a/run-command.h
+++ b/run-command.h
@@ -485,14 +485,14 @@ typedef int (*task_finished_fn)(int result,
  * API reads that setting.
  */
 extern int run_processes_parallel_ungroup;
-int run_processes_parallel(int n,
-			   get_next_task_fn,
-			   start_failure_fn,
-			   task_finished_fn,
-			   void *pp_cb);
-int run_processes_parallel_tr2(int n, get_next_task_fn, start_failure_fn,
-			       task_finished_fn, void *pp_cb,
-			       const char *tr2_category, const char *tr2_label);
+void run_processes_parallel(int n,
+			    get_next_task_fn,
+			    start_failure_fn,
+			    task_finished_fn,
+			    void *pp_cb);
+void run_processes_parallel_tr2(int n, get_next_task_fn, start_failure_fn,
+				task_finished_fn, void *pp_cb,
+				const char *tr2_category, const char *tr2_label);
 
 /**
  * Convenience function which prepares env for a command to be run in a
diff --git a/t/helper/test-run-command.c b/t/helper/test-run-command.c
index ebda2203408..c431e3094df 100644
--- a/t/helper/test-run-command.c
+++ b/t/helper/test-run-command.c
@@ -192,8 +192,8 @@ static int testsuite(int argc, const char **argv)
 	fprintf(stderr, "Running %"PRIuMAX" tests (%d at a time)\n",
 		(uintmax_t)suite.tests.nr, max_jobs);
 
-	ret = run_processes_parallel(max_jobs, next_test, test_failed,
-				     test_finished, &suite);
+	run_processes_parallel(max_jobs, next_test, test_failed,
+			       test_finished, &suite);
 
 	if (suite.failed.nr > 0) {
 		ret = 1;
-- 
2.38.0.rc2.935.g6b421ae1592